Microelectronics conventionally developed around inorganic materials such as silicon (Si) or gallium arsenide (GaAs). Another route is currently being explored around organic materials, such as polymers, on account of their suitability for large-scale manufacture, their mechanical strength, their flexible structure or even their suitability for re-processing. Screens have thus been designed based on organic diodes (OLEDs) or based on organic thin film transistors (OTFTs). Additionally, the use of layer deposition techniques, by spin-coating for example, by ink jet or by screen printing, is made possible through the use of soluble polymers.
However the deposition of organic material presents a certain number of difficulties. To be more specific, getting a good quality conductive organic layer on a substrate surface is difficult. Indeed, a conductive organic layer is obtained by means of organic crystalline materials. These have, unlike amorphous materials which have a random molecular organization, thereby entailing difficult electronic transmission and therefore poor electrical conduction, a periodic molecular structure that affords reliable and controlled electrical conduction.
However, by studying the electrical properties of a thin layer of crystalline polymer that has been deposited wet for example, on the surface of a substrate, generally speaking chaotic and unpredictable electric current conduction is observed instead of it offering the expected good electrical conductivity.
Indeed, the usual techniques of forming a layer of organic material (ordinarily the deposition of a solution comprising said material diluted in a solvent, followed by the evaporation of the solvent leading to the formation of a layer of crystallized material) not generally allow homogeneous growth of the crystal network on account of the non-homogeneity of the substrate surface. For example, the substrate surface has rough patches, a non-homogeneous surface energy, steps or again functional elements such as metal connections for example.
Additionally, non-crystalline organic materials also pose problems when they are deposited also on account of the non-homogeneity of the substrate surface, such as wettability breakdown or stepway problems.